Magnetic domain device having a wide operational temperature range

ABSTRACT

Yttrium-iron magnetic domain materials having bismuth ions on dodecahedral sites are suitable for the manufacture of high-density, high-speed magnetic domain devices for operation at high and especially at very low temperatures. In these devices magnetic domain velocity is greater than 2000 centimeters per second per oersted, and magnetic domain diameter is less than 3 micrometers. A specified operational temperature range may extend from -150 to 150 degrees C.; accordingly, such devices are particularly suitable for operation aboard satellites, e.g., in satellite communications systems.

The Government has rights in this invention pursuant to ContractF33615-81-C-1404 awarded by the Department of the Air Force.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 533,457,filed Sept. 19, 1983 now abandoned which was a continuation-in-part ofapplication Ser. No. 319,609, filed in Nov. 9, 1981, now U.S. Pat. No.4,419,417.

TECHNICAL FIELD

The invention is concerned with magnetic domain or "bubble" devices and,more particularly, with devices having high potential informationdensity and operating speed over an extended operational temperaturerange.

BACKGROUND OF THE INVENTION

Magnetic domain devices are being used primarily as sequential-accessmemory devices in which information is stored in digital form.Functionally, such memory devices may typically comprise a number ofshift registers ("minor loops") each of which is in communication with acommon, "major loop" shift register. Information is represented by thepresence or absence of magnetic domains in a layer of magnetic material,and the function of shifting is effected by means of a magnetic fieldwhich may be controlled as to strength and direction.

In a preferred device structure magnetic domains are nucleated andpropagated in a layer of magnetic garnet material which is deposited ona nonmagnetic garnet substrate having lattice parameters which arecompatible with those of the magnetic layer. Typically, the substrate ismade of gadolinium-gallium garnet material and the magnetic layer ispatterned after yttrium-iron garnet, Y₃ Fe₅ O₁₂ (YIG). Magnetic layersof desirable composition and quality can be deposited on agadolinium-gallium substrate by a process known as liquid phase epitaxy(LPE) as generally described, e.g., by M. H. Randles, "Liquid PhaseEpitaxial Growth of Magnetic Garnets", Crystals for MagneticApplications, Springer, 1978, pp. 71-96.

Magnetic domain propagation paths may be defined in a layer of magneticmaterial, e.g., by a patterned overlying metallic layer or by a patternresulting from selective ion implantation. Representative of the latterapproach are designs as disclosed, e.g., in U.S. Pat. No. 4,249,249,issued Feb. 3, 1981 to P. I. Bonyhard et al. and in the paper by T. J.Nelson et al., "Design of Bubble Device Elements Employing Ion-ImplantedPropagation Patterns", Bell System Technical Journal, Vol. 59 (1980),pp. 229-257.

Desired magnetic anisotropy in a layer of magnetic material results inan "easy direction" of magnetization which is perpendicular to the layerand which renders the layer capable of sustaining magnetic domains whosemagnetization is antiparallel to the magnetization of layer materialsurrounding the domains. Magnetic anisotropy may be "strain induced" asunderstood to be due to an appropriate disparity betweencrystallographic lattice dimensions of supported layer and substrate.Alternatively, anisotropy may be "growth induced" as considered to bedue to local strain or preferential ordering realized upon deposition ofa material in which a crystallographic site such as, e.g., thedodecahedral site is occupied by a mixed ion population. Thisdistinction is made, e.g., in U.S. Pat. No. 3,886,533, issued to W. A.Bonner et al. on May 27, 1975.

Continuing development effort is aimed primarily at reducing magneticdomain size while maintaining or increasing domain wall mobility.Considerable progress has been made towards fast devices having highpacking density as illustrated, e.g., by D. J. Breed et al., "GarnetFilms for Micron and Submicron Magnetic Bubbles with Low DampingConstants", Applied Physics, Vol. 24 (1981), pp. 163-167, and by J. M.Robertson et al., "Garnet Compositions for Submicron Bubbles with LowDamping Constants", Journal of Applied Physics, Vol. 52 (1981), pp.2338-2340.

Recently, a need has arisen for devices to operate in inhospitableenvironments such as, e.g., aboard space stations where operation may berequired over a wide temperature range and, in particular, over a rangewhich extends to very low temperatures.

SUMMARY OF THE INVENTION

It is an object of the invention to provide magnetic domain deviceswhich are operable over a wide temperature range comprising lowtemperatures.

Within the scope of the invention is a magnetic domain device whoseoperation is based on magnetic domains in a supported layer of amagnetic garnet material having uniaxial magnetic anisotropy in adirection which is essentially perpendicular to the layer. Themagnetization of such a magnetic domain is essentially antiparallel tothe magnetization of a portion of the magnetic film surrounding thedomain, the diameter of such a domain is less than 3 micrometers, andthe mobility of a domain is greater than 2000 centimeters per second peroersted.

The device is characterized in that the supported layer consistsessentially of a bismuth-containing garnet material whose composition isessentially as denoted by the formula

    (Y.sub.3-p-q-r-s Bi.sub.p Ca.sub.q RM.sub.r RN.sub.s)(Fe.sub.5-t-u-v-w Al.sub.t Ga.sub.u Si.sub.v Ge.sub.w)O.sub.12

where RM denotes one or several of the magnetic rare earth elements Sm,Eu, Gd, Tb, Dy, Ho, and Er, where RN denotes one or several of thesmall-ionic-radius rare earth elements Lu, Tm, and Yb, and where

p is a preferred range of 0.2-1.5,

q is in a preferred range of 0.2-0.9,

r is in a preferred range of 0.0-0.6,

s is in a preferred range of 0.0-0.6,

t is in a preferred range of 0.0-1.0,

u is in a preferred range of 0.0-1.0,

v is in a preferred range of 0.2-0.9,

w is in a preferred range of 0.0-0.9,

and where v+w is approximately equal to q.

The presence of Sm and/or Eu, in combination with small-ionic-radiusrare earth elements Lu, Tm, and/or Yb gives rise to growth-inducedmagnetic anisotropy; the presence of Tb, Dy, Ho, and/or Er reducesmagnetic bubble mobility and also reduces the deflection angle in amagnetic field gradient; and the presence of Gd, Ho, and/or Dydiminishes the temperature dependence of certain magnetic parameterssuch as, in particular, the collapse field.

The resulting devices are suitable for operation over a wide range oftemperatures; specifically, such operational range comprises a range of-150 to 150 degrees C.

Also within the scope of the invention is a method of transmittingsignals involving nucleating, propagating, or detecting magnetic domainsin a layer of magnetic garnet material whose composition is essentiallyas denoted by a formula as stated above, where p, r, s, t, u, and w arein preferred ranges as stated above, where q is in the range of 0.0-0.9and where v is in the range of 0.0-0.9. Nucleating, propagating, ordetecting magnetic domains is in an environment corresponding to aspecified operational temperature range which comprises a temperature inthe range of -150 to 0 degrees C.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows schematically and greatly enlarged a magnetic domain devicein accordance with the invention;

FIG. 2 illustrates a functional relationship between temperature andmagnetic anisotropy for a magnetic layer in accordance with theinvention as compared with a prior art layer; and

FIG. 3 illustrates functional relationships between temperature andstripe width as well as between temperature and collapse field for amagnetic layer in accordance with the invention.

DETAILED DESCRIPTION

FIG. 1 shows a magnetic domain device comprising magnetic garnet layer11. Magnetic domains or bubbles propagate in layer 11 along closed pathsor loops l₁, l₂, . . . , l_(k) which are commonly referred to as minorloops. Bubbles also propagate along closed path or loop L which iscommonly referred to as a major loop. Generator 12 serves to nucleatebubbles and comprises an electrical conductor which is connected to agenerator pulse source 14 which, in turn, is controlled by controlcircuit 15. Also controlled by control circuit 15 is propagation drivesource 17. Detector 13 serves to detect the presence of bubbles inresponse to an electrical pulse in conductor 26; detector 13 is shownconnected to a utilization circuit 18. Bubbles are maintained at anominal diameter by a bias field supplied by source 19. Conductor 20provides for coupling of minor loops l₁, l₂, . . . , l_(k) to major loopL; specifically, when a suitable electrical pulse is supplied bytransfer pulse source 21 to conductor 20, bubbles are transferred fromthe major loop L to minor loops l₁, l₂, . . . , l_(k) in response torotation of an in-plane drive field produced by source 17. Similarly,bubbles are transferred from the minor loops l₁, l₂, . . . , l_(k) tothe major loop L when a suitable pulse is supplied to conductor 25.Control of the transfer function as well as the operations ofgeneration, propagation, and detection is understood to be synchronizedby clock circuitry comprised in control circuit 15. Further structuraldetails of the device in accordance with FIG. 1 can be found in theabove-identified U.S. Pat. No. 4,249,249 and the above-identified paperby T. J. Nelson et al. which are concerned primarily with devices inwhich bubble paths such as minor and major loops are defined by ionimplanted regions. The invention may alternatively be implemented, e.g.,as a device in which such paths are defined by patterned metallicoverlays; see, e.g., A. H. Bobeck et al., "Current-Access MagneticBubble Circuits", Bell System Technical Journal, Vol. 58, No. 6(July-August 1979), pp. 1453-1540.

In accordance with the invention the material of layer 11 is a magneticgarnet material having a composition which is essentially as specifiedabove. The thickness of layer 11 is approximately equal to the desiredbubble diameter which, in the interest of high packing density, is lessthan 3 micrometers. Such small-diameter bubbles in layer 11 have amobility which is greater than 2000 centimeters per second per oersted.

Devices in accordance with the invention are operable over a widetemperature range as stated above and as may be appreciated uponinspection of FIG. 2 and FIG. 3. Specifically, FIG. 2 graphicallyillustrates temperature dependence of magnetic anisotropy K_(u) for abismuth-containing magnetic layer in accordance with the invention andidentified by the nonspecific formula (YBiCa)₃ (FeSi)₅ O₁₂. Alsoillustrated by FIG. 2 is a corresponding relationship for a prior-artmaterial as identified by the nonspecific formula (LuSmCa)₃ (FeVSi)₅O₁₂, and it can be seen that K_(u) is more nearly constant for thematerial of the invention as is desirable in the interest of operationin a wide temperature range. Similarly, FIG. 3 shows a favorabletemperature dependence of stripe width and collapse field for a magneticlayer in accordance with the invention. If a high-temperature range isdesired which is greater still, then t may be chosen less than or equalto 0.6 and u less than or equal to 0.7. Resulting devices are preferablyused where operation up to 200 degrees C. is specified. If, in a devicebased on a gadolinium-gallium garnet substrate, magnetic domain size isdesired to be less than 1 micrometer, then the presence of rare earthelements is preferred. In this case, the magnetic garnet materialpreferably contains magnetic rare earth elements (RM_(r)) in an amountcorresponding to a value of r greater than or equal to 0.1 andnonmagnetic rare earth elements (RN_(s)) in an amount corresponding to avalue of s greater than or equal to 0.1.

All compositions are understood to allow for small amounts of impuritiesas may unavoidably be present in a deposited layer of magnetic material.It is desirable to minimize the presence of impurities, e.g., lead ispreferably kept below 0.05 atoms per formula unit of garnet, platinumbelow 0.04 atoms per formula unit of garnet, and rhodium, iridium, andcobalt in combination below 0.005 atoms per formula of garnet.

Anisotropy in a magnetic layer of the invention is preferablygrowth-induced; accordingly, approximate matching of lattice constantsat a substrate-layer interface is desirable. Strain-induced contributionto magnetic anisotropy is preferably less than 30 percent and morepreferably less than 15 percent.

Devices of the invention may be used for signal transmission functionssuch as, typically, data storage and retrieval as described above inconnection with FIG. 1, data being represented by the presence orabsence of bubbles in a magnetic layer having a composition as describedabove. In accordance with the invention, such functions are carried outwhen the device is in an inhospitable environment as characterized,e.g., by a specified operational temperature range which comprises atemperature in the range of -150 to 0 degrees C. or at least in therange of -150 to -50 degress C.

The following are examples of typical conditions utilized in thedeposition of garnet epitaxial layers in accordance with the inventionby liquid phase epitaxy.

EXAMPLE 1

A circular gadolinium-gallium garnet substrate measuring approximately2.0 inches in diameter and 20 mils in thickness was used as a depositionsubstrate. The substrate was cleaned, dried, and inserted in a substrateholder of apparatus equipped with a platinum crucible containing apreviously prepared melt. The melt had been obtained by melting 2.39grams Y₂ O₃, 292 grams Bi₂ O₃, 1.135 grams CaO, 5 grams SiO₂, 66.1 gramsFe₂ O₃, and 638 grams PbO; the melt was heated by resistance-heatingcoils to a temperature of approximately 1000 degrees C. The melt wasallowed to react at this temperature for a period of approximately 16hours.

The temperature of the melt was then lowered to a growth temperature ofapproximately 780 degrees C. and the substrate was lowered to within 1centimeter of the melt surface. The substrate was maintained in thisposition for approximately 6 minutes. The substrate was then immersedapproximately 2 centimeters deep into the melt and rotated at a rate of100 RPM. Immersion was for a duration of approximately 1 minute, and thesubstrate was then removed from the melt to a position 1 centimeterabove the melt while rotation continued. The rotation rate was thenincreased to 400 RPM for a period of approximately 30 seconds. Therotation was stopped, and the substrate was withdrawn further at a rateof approximately 0.5 centimeters per minute.

By standard measurement techniques the following physical propertieswere determined for the deposited layer: A layer thickness ofapproximately 1.15 micrometers, a magnetic domain stripe width ofapproximately 1 micrometer, a saturation magnetization (commonlydesignated as 4πM_(s)) of approximately 775 gauss, an anisotropy field(commonly designated as H_(k)) of approximately 1800 oersteds, amaterial length parameter (commonly designated as l) of approximately0.11 micrometer, a lattice constant (commonly designated as a_(o)) ofapproximately 12.930 Angstroms, and a uniaxial anisotropy (commonlydesignated as K_(u)) of approximately 55,500 erg/cm³.

Composition of the layer was determined as represented approximately bythe formula

    {Y.sub.1.9 Bi.sub.0.5 Ca.sub.0.6 }(Fe.sub.4.4 Si.sub.0.6)O.sub.12,

and its magnetic anisotropy was found to vary as a function oftemperature as represented in FIG. 2.

EXAMPLE 2

A circular gadolinium-gallium garnet substrate measuring approximately2.0 inches in diameter and 20 mils in thickness was used as a depositionsubstrate. The substrate was cleaned, dried, and inserted in a substrateholder of apparatus equipped with a platinum crucible containing apreviously prepared melt. The melt had been obtained by melting 3 gramsY₂ O₃, 400 grams Bi₂ O₃, 2 grams CaO, 4.8 grams SiO₂, 8 grams GeO₂, 92grams Fe₂ O₃, and 800 grams PbO; the melt was heated byresistance-heating coils to a temperature of approximately 1000 degreesC. The melt was allowed to react at this temperature for a period ofapproximately 16 hours.

The temperature of the melt was then lowered to a growth temperature ofapproximately 800 degrees C. and the substrate was lowered to within 1centimeter of the melt surface. The substrate was maintaned in thisposition for approximately 6 minutes. The substrate was then immersedapproximately 2 centimeters deep into the melt and rotated at a rate of100 RPM. Immersion was for a duration of approximately 1.5 minutes, andthe substrate was then removed from the melt to a position 1 centimeterabove the melt while rotation continued. The rotation rate was thenincreased to 400 RPM for a period of approximately 30 seconds. Therotation was stopped, and the substrate was withdrawn further at a rateof approximately 0.5 centimeters per minute.

By standard measurement techniques the following physical propertieswere determined for the deposited layer: A layer thickness ofapproximately 1.85 micrometers, a magnetic domain stripe width ofapproximately 1.65 micrometers, a saturation magnetization ofapproximately 535 gauss, an anisotropy field of approximately 1725oersteds, a material length parameter of approximately 0.205 micrometer,a lattice constant of approximately 12.384 Angstroms, and a uniaxialanisotropy of approximately 31,500 erg/cm³.

Composition of the layer was determined as represented approximately bythe formula

    {Y.sub.2.0 Bi.sub.0.3 Ca.sub.0.7 }(Fe.sub.4.3 Si.sub.0.4 Ge.sub.0.3)O.sub.12,

and its collapse field and stripe width were found to vary as a functionof temperature as represented by FIG. 3.

EXAMPLE 3

A circular gadolinium-gallium garnet substrate approximately 2.0 inchesin diameter and 20 mils in thickness was used as a deposition substrate.The substrate was cleaned, dried, and inserted in a substrate holder ofapparatus equipped with a platinum crucible containing a previouslyprepared melt. The melt had been obtained by melting 2.82 grams Y₂ O₃,398 grams Bi₂ O₃, 1.00 gram Sm₂ O₃, 3.20 grams Lu₂ O₃, 1.04 grams CaO,6.50 grams SiO₂, 113.2 grams Fe₂ O₃, and 1033.6 grams PbO; the melt washeated by resistance-heating coils to a temperature of approximately1000 degrees C. The melt was allowed to react at this temperature for aperiod of approximately 16 hours.

The temperature of the melt was then lowered to a growth temperature ofapproximately 803 degrees C. and the substrate was lowered to within 1centimeter of the melt surface. The substrate was maintained in thisposition for approximately 6 minutes. The substrate was then immersedapproximately 2 centimeters deep into the melt and rotated at a rate of100 RPM. Immersion was for a duration of approximately 10 seconds, andthe substrate was then removed from the melt to a position 1 centimeterabove the melt while rotation continued. The rotation rate was thenincreased to 400 RPM for a period of approximately 30 seconds. Therotation was stopped, and the substrate was withdrawn further at a rateof approximately 0.5 centimeters per minute.

By standard measurement techniques the following physical propertieswere determined for the deposited layer: A layer thickness ofapproximately 0.56 micrometers, a magnetic domain stripe width ofapproximately 0.64 micrometers, a saturation magnetization ofapproximately 1264 gauss, a collapse field of approximately 605oersteds, a material length parameter of approximately 0.076 micrometer,a lattice constant of approximately 12.4017 Angstroms, a uniaxialanisotropy of approximately 103,000 erg/cm³, and a wall energy ofapproximately 0.96 erg/cm².

Composition of the layer was determined as represented approximately bythe formula

    {Y.sub.1.3 Bi.sub.0.7 Ca.sub.0.3 Sm.sub.0.25 Lu.sub.0.5 }(Fe.sub.4.7 Si.sub.0.3)O.sub.12.

EXAMPLE 4

A circular gadolinium-gallium garnet substrate approximately 2.0 inchesin diameter and 20 mils in thickness was used as a deposition substrate.The substrate was cleaned, dried, and inserted in a substrate holder ofapparatus equipped with a platinum crucible containing a previouslyprepared melt. The melt had been obtained by melting 2.05 grams Y₂ O₃,300 grams Bi₂ O₃, 0.44 gram Gd₂ O₃, 0.164 gram Ho₂ O₃, 2.00 grams CaO,3.25 grams GeO₂, 5.75 grams SiO₂, 116 grams Fe₂ O₃, and 850 grams PbO;the melt was heated by resistance-heating coils to a temperature ofapproximately 1000 degrees C. The melt was allowed to react at thistemperature for a period of approximately 16 hours. The temperature ofthe melt was then lowered to a growth temperature of approximately 833degrees C. and the substrate was lowered to within 1 centimeter of themelt surface. The substrate was maintained in this position forapproximately 2.75 minutes. The substrate was then immersedapproximately 2 centimeters deep into the melt and rotated at a rate of100 RPM. Immersion was for a duration of approximately 10 seconds, andthe substrate was then removed from the melt to a position 1 centimeterabove the melt while rotation continued. The rotation rate was thenincreased to 400 RPM for a period of approximately 30 seconds. Therotation was stopped, and the substrate was withdrawn further at a rateof approximately 0.5 centimeters per minute.

By standard measurement techniques the following physical propertieswere determined for the deposited layer: A layer thickness ofapproximately 2 micrometers, a saturation magnetization of approximately562 gauss, a collapse field of approximately 1500 oersteds, a materiallength parameter of approximately 0.18 micrometer, a lattice constant ofapproximately 12.384 Angstroms, and a uniaxial anisotropy ofapproximately 33,500 erg/cm³.

A similarly grown second layer was determined to have -0.21 percent perdegree C. normalized temperature dependence of the collapse field and alinewidth of 370 oersteds.

Composition of the layers was determined as represented approximately bythe formula

    {Y.sub.1.5 Bi.sub.0.5 Gd.sub.0.1 Ho.sub.0.2 Ca.sub.0.7 }(Fe.sub.4.3 Si.sub.0.4 Ge.sub.0.3)O.sub.12.

What is claimed is:
 1. Device comprising a supported layer of a magneticgarnet material having uniaxial magnetic anisotropy in a direction whichis essentially perpendicular to said layer,said layer being capable ofsustaining a magnetic domain whose magnetization is essentiallyantiparallel to the magnetization of a portion of said layer surroundingsaid domain, said domain having a diameter which is less than 3micrometers, and said domain having mobility which is greater than 2000centimeters per second per oersted, said device being CHARACTERIZED INTHAT the composition of said garnet material is essentially as denotedby the formula

    (Y.sub.3-p-q-r-s Bi.sub.p Ca.sub.q RM.sub.r RN.sub.s)(Fe.sub.5-t-u-v-w Al.sub.t Ga.sub.u Si.sub.v Ge.sub.w)O.sub.12

where RM denotes one or several of the magnetic rare-earth elements Sm,Eu, Gd, Tb, Dy, Ho, and Er, where RN denotes one or several of thesmall-ionic-radius rare-earth elements Lu, Tm, and Yb, p is in the rangeof 0.2-1.5, q is in the range of 0.2-0.9, where r is in the range of0.0-0.6, s is in the range of 0.0-0.6, t is in the range of 0.0-1.0, uis in the range of 0.0-1.0, v is in the range of 0.2-0.9, w is in therange of 0.0-0.9, and where v+w is essentially equal to q whereby saiddevice has an operational temperature range which comprises the range of-150 to 150 degrees C.
 2. Device of claim 1 in which said layer has amagnetic anisotropy which is predominantly as growth induced, an amountof less than 30 percent of said anisotropy being strain induced. 3.Device of claim 1 in which said garnet material comprises less than 0.05atoms of lead per formula unit of garnet, less than 0.04 atoms ofplatinum per formula unit of garnet, and less than 0.005 atoms ofrhodium, iridium, and cobalt in combination per formula unit of garnet.4. Device of claim 1 in which aluminum is present in said layer in anamount corresponding to a value of t less than or equal to 0.6, in whichgallium is present in said layer in an amount corresponding to a valueof u less than or equal to 0.7, whereby said device has an operationaltemperature range which comprises the range of -150 to 200 degrees C. 5.Device of claim 1 in which said diameter is less than 1 micrometer, inwhich said layer is supported by a gadolinium-gallium garnet substrate,in which said layer comprises one or several magnetic rare earthelements corresponding to a value of r greater than or equal to 0.1, andin which said layer comprises one or several nonmagnetic rare earthelements corresponding to a value s greater than or equal to 0.1. 6.Method for transmitting signals, said method comprising nucleating,propagating, or detecting magnetic domains in a supported layer of amagnetic garnet material having uniaxial magnetic anisotropy in adirection which is essentially perpendicular to said layer,said layerbeing capable of sustaining a magnetic domain whose magnetization isessentially antiparallel to the magnetization of a portion of said layersurrounding said domain, said domain having a diameter which is lessthan 3 micrometers, and said domain having mobility which is greaterthan 2000 centimeters per second per oersted, said method beingCHARACTERIZED IN THAT the composition of said garnet material isessentially as denoted by the formula

    (Y.sub.3-p-q-r-s Bi.sub.p Ca.sub.q RM.sub.r RN.sub.s)(Fe.sub.5-T-u-v-w Al.sub.t Ga.sub.u Si.sub.v Ge.sub.w)O.sub.12

where RM denotes one or several of the magnetic rare-earth elements Sm,Eu, Gd, Tb, Dy, Ho, and Er, where RN denotes one or both of thesmall-ionic-radius rare-earth elements Tm, Yb, and Lu, where p is in therange of 0.2-1.5, q is in the range of 0.1-0.9, r is in the range of0.0-0.6, s is in the range of 0.0-0.6, t is in the range of 0.0-1.0, uis in the range of 0.0-1.0, v is in the range of 0.0-0.9, w is in therange of 0.0-0.9, and where v+w is essentially equal to q, and saidnucleating, propagating, or detecting being in an environmentcorresponding to a specified operational temperature range whichcomprises a temperature in the range of -150 to 0 degrees C.
 7. Methodof claim 6 in which said specified operational temperature rangecomprises a temperature in the range of -150 to -50 degrees C.